morgan



B. MORGAN.

CUTTING DIE AND METHOD OF MAKING THE SAME. APPLICATION FILED 050.24.1911.

71,315,030. Patented Sept. 2,1919.

ATTORNEYS BERNARD, MoneAn -on KEENaE, New nannsnurnnh cu r'rlnegmn ANDfME'II-IOD OFMEAKING THE SAME.

To all whom it may concern:

Be it known that I, BERNARD MORGAN, a subject of the British Empire,.residing at Keene, New Hampshire; in the county'of Cheshire, State of New Hampshire qhave invented certain new and useful Improve:- ments in Cutting-Dies and Methods of Mak ing the Samegand I dohereby declare the following to be a full, clear; and exact description of the invention, suchas wlll enable others skilled in the art to which it appertains to make and use thesame.

This invention relates to improvements in thread cutting dies andmethod of making the same, and has for its rincipal obj ectto provide a method of manufacture and design of die whereby the quantity of material' used for the die and the labor required for its manufacture may both be materia-llv reduced with a consequent large savingin manufacturing cost. y y i It is well known that high speech steel is far superior to other kinds of "steels for machine tools but it hasheretofore been-used but little for the manufacture ofthread cutting dies, because of its excessive cost, but by my improved methodand designthe-cost is very little if any more than for dies of prior designsmadeofordinary steel. y

A further object of" my invention is to provide a die of improveddesignpo ssessing several important advantages overdiesof existing types. y L My improved die consists essentially ofa sheet metal disk or ringwiththethre-adcutters projecting from the edge of the ring and shaped from the metal. ofthe ringm such manner that the length i of the cutter not determined by the thickness of the metal as in ordinary dies but instead the cutters may he as long as necessary with the thinnest metal having s'u'fficient tensilest'rength for the purpose;

One advantage of my improved die isthat more cutting edges may be provided than have heretofore been employed; Another important advantage is that the die isselfclearing that is, thecutting edges whenrotated in the direction of the out tend to bite into the work, but when rotated in'the; reverse direction the cutting edges tendto release themselveswith the resultthat the die may be screwed oil the thread withoutwearing the thread down and distorting it, as as uently "happens with ordinary dies, parti'cu arly in cutting threadson soiitmetals.

Specification of Letters Patent.

Patented sept. 2, 19119.

Application filed December 24; 1917. Serial No. 208,564:

Another important advantageofmy improved: die is that the i cutters may he inie-- gral with a continuous supporting ring and yet so arranged that they may be adjusted toward ithe-center to compensate for; the wear of' thecutting edges a In the accompanying drawings; I have disclosed two types of my improved die and also the important steps in its process of manufacture, and in said drawings- Figure 1 is a plan view showingthe PHHOllGClL blank from whiclr a die for externali threadslisformed; j

Fig. 2isaview similan to Fig, 1, showing the die after formation of the outtersthere Fig. 3isaanenlarged view of portion of Fig. '2showing the cutters-in greatei detail and also illustrating the method of adjusting the cutters to compensate for wear;

Fig. i is a verticalsection of the die on the same scale as Fig. 3; i l a a Fig. 5is a perspective view ofthecompleteddie; i

Fig. 6 isa perspective view 0f a-tap de signed for internallthreads; and

Fig. 7 is a detail View of a modifiedlconstruetion. i

The blanks for forming dies for external threads: are out from sheetsofsuitable steel by an ordinarypunch press to theshape shownin Fig. lgthat is, theeut blank consists ofanouter ring 2 ofa' diameterto fit the chuck Or stock in which it is to "be used and anumber of tongues 4: projectingjlrom the inner edge of the ring. Thering-niay also. be formed with several spaced holes 3 for locking it" against rotation inthe chuck or holder; or it may he held in the same manner as heretofore employed for; ordinary dies. The tongues 4 areof a width equal to the desired lengthof the cutting edge and extend toward'the center to a pointsomewhat greater thanthe radius of the thread.

which they are designed to out. In the drawing s1X tongues are shownlbut the numher may of course, lJQVELIlGd IIIOIG or less.

After the blank is out and before the metal is tempered, the tongnes are individually twisted to bring their inner edges intoa plane approximately at" right angles to thef'ace of" the ring: At thesame time thejedgesof" the tongues are shifted somewhat of? center 'or forward against the rotation or eut all in the same direction,

the" shifting of the tongues ofi' center osing the tongues tend to and away from the centerso that the die unscrews without distorting the previously before the metal is tempered.

as shown in Fig. 7 3. A bar 7 width is inserted between theteeth with one preferably accomplished at the same operation as the twisting of the tongues. The degree to which the tongues are shifted may be varied more or less as experience determines. Both operations may be performed by a shaping press, the final position of the tongues being such that one edge of the end face of each tongue coincides approximately with the radial line through the center of the base of the tongue as indicated in Fig.

3, wherein the radial center line is shown at 0 0.

After the tongues are twisted to the proper position they will be cut to form the usual thread cutting teeth, that is, their ends will be serrated with each serration from one side to the other slightly more projected than the next serration and with the edges of the serrations inclined somewhat-from the circumferential so that the corners of theiteeth on the advancing edge of the cutters will bite into the metal when the die is rotated in the direction of the arrow inFig. 3. v

The teeth will usually be cut in the edges of tongues after the twisting operation but of the steps is not, however, essential,- as the teeth may be cut before the twisting or after the twisting and tempering.

In operation the die will be rotated in the direction of the arrow in. Fig. 3, with the corners of the teeth marked at acting as the cutting edges so that the line of thrust from the cutting edge to the supporting ring will be off center as indicated by the dotted line 6 e. The effect of this is to cause the tongues which are somewhat elastic, to tend to straighten toward the radial and enter the metal. -On the reverse direction of rotation, as the die unscrewed,

bend toward the ring out threads.

As the cuttingedges wear away the increasing circumference maybe compensated for by slightly straightening the tongues of proper edge'against the base at the rear edge of onetongue and. its opposite edge, near the outer endrof the adjacenttongue. I By twisting the bar in the direction shown, the tooth will be forced back or slightly straightened to thereby reduce the, distance between the opposite cutters, and cause the teeth to? enter deeper into themetal.

Thread cutting dies of the common type are made by cutting from a bar or rod of rolledsteel a piece equal to the length of the cutters, and

machining into shape with the teeth running 'circumferentially of the rod. In a rolled'steel barthe grain of the metalextends longitudinallyv of the'bar, so

This order tent of the twist of the ends of the cutters.

that the teeth of the die are cut across the grain of the metal and are consequently materially weaker than if extending with the grain. Further, it is well known that the metal of the central section is inferior in strength and toughness to the metal near the surface, and in shaping the dies from the rod section the teeth come in the worst part of the metal and it is usual to find most threading dies, after a very little use, with one or more teeth broken. In sheet steel the surface or skin portion is always the tough or strong metal and in my improved design the cutting edges are directly on such surface.

In Fig. 7 I have illustrated a simple method of making a die adjustable to take up wear or accommodate slight variations in the diameter of the work to be threaded. As here shown, the ring 2 is provided with a tapered hole 15 at one point in its pe riphery and is then cut radially across the hole as indicated at 16, forming an expansible ring similar to the. split ring of a clutch.

In supporting this ring in a chuck a screw terminating in a tapered pin will be threaded in the chuck with its axis parallel with the axis of rotation of the die and arranged so as to be forced against the tapered hole when the die is held in the chuck. will be initially set in sufiiciently to the ring so that as the teeth wear may be slightly retracted, allowing the ring to contract and thus reduce the diameter of the cutting edges to compensate for the wear. By this means a quicker adjustment of the cutters may be had than can beeffected by springing each individual cutter in the manner above described.

In describing my improved die, I have stated that the ends of the cutters were twisted through approximately a quarter turn and. that the teeth extended in substan- The pin expand the pin tially the plane of the annulus. It will of course be understood that it is not essential that either of these angles be exact. The excutters may vary considerably so long as the teeth are cut with the proper angle to the axis of rotation ,to give the desired pitch to the thread. That is to say, it is not necessary that the teeth be at a definite angle to the facesof the twisted The teeth may extend at a greater or less angle than the angle or pitch of the thread without affecting the operation of the cutter. In the same way, the teeth need not be at the exact angle of the pitch of the thread to the plane of the annulus, as the annulus may itself be clamped in the chuck at an angle to the axis of rotation.

It is of course desirable, however, that the teeth becut at an angle to the annulus equal to the pitch of the thread so that the annulusmay be clamped in the chuck in a plane normal to the axis of rotation.

Dies or taps for internal threads may also be made according to my invention. Such a die is shown in Fig. 6 and comprises a middle disk or body portion 10 having tongues 11 projecting from its edge. The tongues are twisted in the manner shown to bring the outer ends of the tongues transverse to the plane of the disk and oil'set from the radial in the same manner as the cutters of the die for cutting external threads. The end faces of the tongues are provided with the usual serrations or thread-cutting teeth 12 shaped to cut when the die is rotated in the direction of the arrow and to release when rotated in the opposite direction.

The body 10 will be provided with a suit able opening 13 by means of which it may be attached to the cutter head, or any other usual or suitable means may be provided for the urpose. a

The cutters o f this type of die may be ad justed or set from time to time to conr pensate for wear in the same manner as the cutters of the other die.

It is, of course, understood that invention is not limited to the details of design shown and described herein, for, so far as I am aware, I am the first to devise a die and a method of manufacture therefor whereby high speed steel or sheet material of any, kind, may be used for the metal of the die with the attendant advantages above enumerated.

I claim:

1. The method of making a thread cutting die which consists in cuttlng from a sheet of steel a die member having fiat cutter 'forming projections and then turning or twisting said projections to bring their fiat faces approximately transverse of the plane of the sheet.

2. The method of making a thread cutting die which consists in cuttlng from a sheet of steel a die member having flat cutter forming projections and then turning or twisting said projections to bring their flat faces approximately transverse of the plane of the sheet, thereafter tempering said projections to form cutting edges,

3. The method of forming a thread cutting die which consists in cutting from a metal sheet an annular die member having cutters extending radially of said body portion, each projection comprising a base integral with the annulus and a cutting edge turned at approximately right angles to the base. i

5. A thread cutting die comprising an annular body portion of sheet metal, thread cutters extending radially of said body portion, each projection comprising a base integral with the annulus, and a cutting edge turned approximately at right angles .to the base and offset radially so that the radial line passing through the middle of the base lies to one side of the middle of the cutting edge.

6. A thread cutting die consisting of an annulus of sheet steel with the plane of the sheet intersecting the center of the annulus, a series of cutters projecting radially within said annulus, each cutter having its base portion integral with said annulus and its free end turned at right angles to the base portion, and provided with thread cutting teeth or serrations approximately parallel with the plane of the annulus whereby the length of the cutters is determined by the width of the projection.

In testimony whereof I aflix my signature.

. BERNARD MORGAN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

